dispatch: check shell alias again after loading extensions (issue4355)

Before this patch, the shell alias causes failure when it takes its
specific (= unknown for "hg") options in the command line, because
"_parse()" can't accept them.

This is the regression introduced by 03d345da0579.

It fixed the issue that ambiguity between shell aliases and commands
defined by extensions was ignored. But it also caused that ambiguous
shell alias is handled in "_parse()" even if it takes specific options
in the command line.

To avoid such failure, this patch checks shell alias again after
loading extensions.

All aliases and commands (including ones defined by extensions) are
completely defined before the 2nd (= newly added in this patch)
"_checkshellalias()" invocation, and "cmdutil.findcmd(strict=False)"
can detect ambiguity between them correctly.

For efficiency, this patch does:

  - omit the 2nd "_checkshellalias()" invocation if "[ui] strict= True"

    it causes "cmdutil.findcmd(strict=True)", of which result should
    be equal to one of the 1st invocation before adding aliases

  - avoid removing the 1st "_checkshellalias()" invocation

    it causes "cmdutil.findcmd(strict=True)" invocation preventing
    shell alias execution from loading extensions uselessly

mercurial/dispatch.py

@@ -644,6 +644,7 b' def _checkshellalias(lui, ui, args, prec'
         return
 
     if precheck:
+        strict = True
         norepo = commands.norepo
         optionalrepo = commands.optionalrepo
         def restorecommands():
@@ -652,13 +653,14 b' def _checkshellalias(lui, ui, args, prec'
         cmdtable = commands.table.copy()
         addaliases(lui, cmdtable)
     else:
+        strict = False
         def restorecommands():
             pass
         cmdtable = commands.table
 
     cmd = args[0]
     try:
-        aliases, entry = cmdutil.findcmd(cmd, cmdtable)
+        aliases, entry = cmdutil.findcmd(cmd, cmdtable, strict)
     except (error.AmbiguousCommand, error.UnknownCommand):
         restorecommands()
         return
@@ -715,6 +717,14 b' def _dispatch(req):'
 
     addaliases(lui, commands.table)
 
+    if not lui.configbool("ui", "strict"):
+        # All aliases and commands are completely defined, now.
+        # Check abbreviation/ambiguity of shell alias again, because shell
+        # alias may cause failure of "_parse" (see issue4355)
+        shellaliasfn = _checkshellalias(lui, ui, args, precheck=False)
+        if shellaliasfn:
+            return shellaliasfn()
+
     # check for fallback encoding
     fallback = lui.config('ui', 'fallbackencoding')
     if fallback:

tests/test-alias.t

@@ -353,7 +353,7 b' command provided extension, should be ab'
   > [extensions]
   > hgext.rebase =
   > [alias]
-  > rebate = !echo this is rebate
+  > rebate = !echo this is \$HG_ARGS
   > EOF
   $ hg reba
   hg: command 'reba' is ambiguous:
@@ -361,6 +361,8 b' command provided extension, should be ab'
   [255]
   $ hg rebat
   this is rebate
+  $ hg rebat --foo-bar
+  this is rebate --foo-bar
 
 invalid arguments